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HW2_Light_SOLUTIONS

# HW2_Light_SOLUTIONS - ASTR302 Homework#2(due in class on...

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ASTR302 Homework #2 (due in class on Wednesday, January 30, 2008) 1) Complete the Lecture Tutorial on Telescopes and Earth’s Atmosphere (pp 49-51). 2) Complete the Lecture Tutorial on Light and Atoms (pp 63-67). 3) Consider a hydrogen atom in the second excited state (n=3). Include an energy diagram with your solution to each of the following scenarios. a. If the excited atom returns to the ground state, what is the wavelength of the photon given off by the atom? b. What is the wavelength of a photon that would just barely ionize the hydrogen atom in the excited state (n=3), assuming all of the photon energy is transferred to the atom? 3a) We need to compare the energy level of the electron in the n=3 excited state with the electron in the n=1 ground state. ( 29 ( 29 nm m x eV s m x eV J x eV hc hc eV eV E E c h hf n m eV E E n m 5 . 102 10 03 . 1 1 . 12 / 10 3 * 19J - 1.602x10 1 * sec) 10 623 . 6 ( 1 . 12 1 . 12 ) 889 . 0 ( * ) 6 . 13 ( 1 1 3 1 * 6 . 13 1 1 * 6 . 13 7 8 34 2 2 1 3 2 2 = = = = = = - - = - - = - = = - - = - - - λ λ λ Thus, a UV photon of wavelength 102.5 nm is given off by the hydrogen atom when an electron in the n=3 excited state falls to the ground state (n=1). 3b) Ionizing the atom involves the electron being excited to the n = : ( 29 nm m x eV s m x eV J x eV hc hc eV eV E E 8 . 820 10 2 . 8 51 . 1 / 10 3 * 19J - 1.602x10 1 * sec) 10 623 . 6 ( 51 . 1 51 . 1 ) 111 . 0 ( * ) 6 . 13 ( 1 3 1 * 6 . 13 7 8 34 2 2 3 = =

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HW2_Light_SOLUTIONS - ASTR302 Homework#2(due in class on...

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